1. Field of the Invention
Embodiments of the present invention generally relate to polishing a substrate, such as a semiconductor wafer.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a feature side, i.e., a deposit receiving surface, of a substrate. As layers of materials are sequentially deposited and removed, the feature side of the substrate may become non-planar and require planarization and/or polishing. Planarization and polishing are procedures where previously deposited material is removed from the feature side of the substrate to form a generally even, planar or level surface. The procedures are useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, and scratches. The procedures are also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing.
Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a semiconductor wafer by moving the feature side of the substrate in contact with a polishing pad while in the presence of a polishing fluid. Material is removed from the feature side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity.
Periodic conditioning of the polishing surface is required to maintain a consistent roughness and/or a generally flat profile across the polishing surface. The conditioning is typically performed using a rotating conditioning disk that is urged against the polishing surface while being swept across the majority of the pad surface. However, the conditioning disk may not be utilized effectively on the outer peripheral edge of the pad surface as the disk may cut into the pad and cause a condition known as “edge balding,” where the peripheral edge of the pad is worn away prematurely. Likewise, the peripheral edge of the pad may not be utilized for polishing as the peripheral edge of the pad is not conditioned to the same degree as portions of the pad interior of the peripheral edge.
Therefore, there is a need for a method and apparatus that facilitates equalized conditioning of the polishing surface and enables global utilization of the polishing surface of the pad.